When light passes through sequential interfaces, there may be a change of phase upon reflection at each interface. Additionally the wavelength changes with each change of the index of refraction. If the thickness of a thin layer is chosen correctly, then it will serve as an anti-reflective coating bringing about maximally destructive interference between the first and second reflected waves. For convenience, the index of refraction for a variety of materials is provided below. Materials at 20°C for light with a vacuum wavelength of 589 nm.
Material n Material n Material n
benzene 1.501 diamond 2.419 plexiglas 1.51
carbon disulfide 1.628 fluorite (CaF) 1.434 quartz (crystalline) 1.544.
carbon tetrachloride 1.461 glass (crown) 1.52 quartz (fused) 1.458
ethanol 1.361 glass (flint) 1.66 sodium chloride 1.544
glycerine 1.473 ice (0°C) 1.309 zircon 1.923
water (fresh) 1.333 polystyrene 1.49 air 1.00029
Part (a) If the light passes from water, through a thin layer of diamond, and then into zircon, then The first phase change is the second is
Part (b) If the wavelength of the incident light in water is , then the wavelength of the same light while traveling in diamond is .